Pierre Gaston writes:
> On Tue, Aug 26, 2008 at 4:49 PM, R. Bernstein <[EMAIL PROTECTED]> wrote:
> > Pierre Gaston writes:
> > > On Tue, Aug 26, 2008 at 5:41 AM, R. Bernstein <[EMAIL PROTECTED]> wrote:
> > > > Both zsh and ksh have a way to open a file or duplicate a file
> > > > descriptor and let the interpreter pick the descriptor saving the
> > > > newly-allocated file descriptor number in a variable. In particular:
> > > >
> > > > exec {fd}<&0
> > > >
> > > > will duplicate stdin and save the newly allocated file-descriptor
> > > > number to fd. Also:
> > > >
> > > > exec {fd}<filename
> > > >
> > > > opens filename with a new file descriptor and saves the number
> > > > allocated in fd. Short of going outside of the language and using
> > > > lsof, /proc, or the processes table, I haven't been able to figure out
> > > > how to do the corresponding thing in bash. Is there a way?
> > > >
> > > > If not, it would be great if a future version had this extension that
> > > > zsh and ksh both seem to have.
> > > >
> > > > Thanks!
> > >
> > > This is a standard behaviour and you can do this in pretty much any
> > > shell out there, including bash.
> >
> > Really? It doesn't seem to be documented in bashref. And when I tried just
> > a moment ago:
> >
> > $ {fd}<&0
> > {fd}<&0
> > bash: {fd}: command not found
> > $ bash --version
> > bash --version
> > GNU bash, version 3.2.39(1)-release (i486-pc-linux-gnu)
> >
> > Perhaps you are thinking of the variation without braces?
> >
>
> well, I was thinking of the normal redirection syntax:
> exec 3<&0
>
> I doubt '{fd}<&0' is meaningfull anywhere.....in ksh {fd} tries to
> run the command {fd} like in bash
> in zsh it tries to run the command "fd"
> What are you talking about???
>
I suppose this is new enough stuff that you would need recent ksh
or zsh version to see it. From a recent ksh 93t manual:
If one of the above, other than >&- and the ># and ># forms, is
preceded by ing space, then a file descriptor number > 10 will
be selected by the shell and stored in the variable varname.
If >&- or the any of the ># and ># forms is preceded by
{varname} the value of varname defines the file descriptor to
close or position. For example:
... 2>&1
means file descriptor 2 is to be opened for writing as a duplicate of
file descriptor 1 and
exec {n}<file
means open file named file for reading and store the file descriptor
number in variable n.
zsh has something similar.
